Polarized light irradiating apparatus and method of irradiating polarized light for photo alignment

ABSTRACT

A polarized light irradiating method includes a first movement step and a second movement step. The first movement step includes a step (a) of moving a first stage from a first position to the irradiation area and irradiating a polarized light onto a first substrate mounted on the first stage, and a step (b) of returning the first stage to the first position from the irradiation area. The second movement step includes a step (c) of moving a second stage from a second position to the irradiation area and irradiating the polarized light onto a second substrate mounted on the second stage, and a step (d) of returning the second stage to the second position from the irradiation area. The step (c) follows after beginning of the step (b). The step (a) follows after beginning of the step (d).

CROSS-REFERENCES TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 14/735,956 filed onJun. 10, 2015, which is a continuation of U.S. application Ser. No.14/201,159 filed on Mar. 7, 2014, now U.S. Pat. No. 9,354,472, thecontents of which, including specification, claims and drawings, areincorporated herein by reference in their entirety. This applicationclaims priority from Japanese Patent Application Serial No. 2013-047350filed on Mar. 8, 2013, the contents of which, including specification,claims and drawings, are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a polarized light irradiatingtechnology to be performed for photo alignment.

2. Background Art

In recent years, a technology referred to as Photo Alignment which is atechnology for performing alignment by light irradiation when obtainingan alignment layer in an alignment film or an angle of view fieldcompensation film of an liquid crystal display device exemplifiedprincipally by a liquid crystal panel has started to be employed.Hereinafter, the film or the layer in which alignment is caused by usingthe light irradiation is collectively referred to as photo alignmentfilm. The term “alignment” or “alignment process” means giving adirectional property to a certain property of an object.

Photo alignment is achieved by irradiating a film for photo alignment(hereinafter, referred to as a “film material”) with polarized light.The film material is formed of a resin such as polyimide, and the filmmaterial is irradiated with polarized light polarized in a desireddirection (the direction to be aligned). With an irradiation ofpolarized light having a predetermined wavelength, a molecular structure(for example, a side chain) of the film material is aligned with thedirection of the polarized light, so that a photo alignment film isobtained.

The photo alignment film is increased in size in association with anincrease in size of liquid crystal panel in which the photo alignmentfilm is used. Therefore, a required width of the irradiation area of thepolarized light is increased to 1500 mm or wider. Examples of thepolarized light irradiating apparatuses having a wide irradiation areaincludes an apparatus disclosed in Japanese Patent No. 4815995. Theapparatus includes a rod-like light source having a length correspondingto the width of the irradiation area, and a wire grid polarized lightelement configured to polarize light from the light source, and isconfigured to irradiate a film material transported in a directionorthogonal to the longitudinal direction of the light source withpolarized light.

In the polarized light irradiating apparatus for photo alignmentdescribed above, there are a case where an object (work) of thepolarized light irradiation is a film material having a continuouslyextending elongated shape (hereinafter, referred to as an elongatedwork), and a case where a film material is already provided on a liquidcrystal substrate and hence the liquid crystal substrate with a filmmaterial is a work.

Japanese Patent No. 4815995 discloses an apparatus in which theelongated work is wound into a roll, and an elongated work drawn fromthe roll is irradiated with polarized light. The elongated workirradiated with the polarized light at the time of roll-to-rolltransport is cut at a predetermined position and adhered to the liquidcrystal substrate. In contrast, as regards the polarized lightirradiating apparatus configured to irradiate the liquid crystalsubstrate with the film material with the polarized light, no CitedReference which discloses a configuration of an apparatus which has aperformance of efficient processing (in a short tact time) is found.

SUMMARY OF THE INVENTION

The invention of this application relates to a polarized lightirradiating method for photo alignment using a polarized lightirradiating apparatus. The apparatus includes an irradiating unitconfigured to irradiate polarized light onto a substrate at anirradiation area; a first stage and a second stage, the substrate isconfigured to be placed on the first stage or the second stage; and astage movement mechanism configured to cause the substrate on the firstor second stage to be irradiated with the polarized light by moving thefirst or second stage to the irradiation area. The stage movementmechanism is configured to move the first stage from a first position atone side of the irradiation area to the irradiation area and to move thesecond stage from a second position at the other side of the irradiationarea to the irradiation area. The stage movement mechanism is configuredto return the first stage to the first position after passage throughthe irradiation area and to return the second stage to the secondposition after passage of the second stage through the irradiation area.The method includes a first movement step and a second movement step.The first movement step includes a step (a) of moving the first stagefrom the first position to the irradiation area and irradiating apolarized light onto a substrate mounted on the first stage, and a step(b) of returning the first stage to the first position from theirradiation area. The second movement step includes a step (c) of movingthe second stage from the second position to the irradiation area andirradiating the polarized light onto a substrate mounted on the secondstage, and a step (d) of returning the second stage to the secondposition from the irradiation area. The step (c) follows after beginningof the step (b). The step (a) follows after beginning of the step (d).

The first stage or a second stage may be a plurality of pins, each ofthe pins comprises a suction hole. The first stage or the second stagemay include an XYθ movable mechanism.

The method may include a first mounting step of mounting a firstsubstrate onto the first stage at the first position before the step(a), and a second mounting step of mounting a second substrate onto thesecond stage at the second position before the step (c). Further themethod may include a first collecting step of collecting the firstsubstrate from the first stage at the first position after the step (b,and a second collecting step of collecting the second substrate from thesecond stage at the second position after the step (d). A time zone ofthe first collecting step and the first mounting step and a time zone ofthe step (c) and the step (d) may partially or entirely overlap. A timezone of the second collecting step and the second mounting step and atime zone of the first movement step may partially or entirely overlap.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of a polarized light irradiatingapparatus for photo alignment according to an embodiment of theinvention;

FIG. 2 is a schematic front view of the polarized light irradiatingapparatus illustrated in FIG. 1;

FIG. 3 is a schematic plan view of a stage movement mechanism 3illustrated in FIG. 1;

FIG. 4 is a schematic perspective view illustrating a mechanism formounting or collecting a substrate S on stages 21 and 22;

FIG. 5 is a perspective view illustrating a schematic configuration of asubstrate aligner 6 provided on the apparatus of the embodiment; and

FIG. 6A is a first drawing for explaining a sequence program mounted ona control unit 4 and schematically illustrating an operation of theapparatus;

FIG. 6B is a second drawing for explaining a sequence program mounted ona control unit 4 and schematically illustrating an operation of theapparatus.

FIG. 6C is a third drawing for explaining a sequence program mounted ona control unit 4 and schematically illustrating an operation of theapparatus.

FIG. 6D is a fourth drawing for explaining a sequence program mounted ona control unit 4 and schematically illustrating an operation of theapparatus.

FIG. 6E is a fifth drawing for explaining a sequence program mounted ona control unit 4 and schematically illustrating an operation of theapparatus.

DETAILED DESCRIPTION OF THE INVENTION

Subsequently, a mode for executing the invention of the presentapplication (hereinafter, referred to as an embodiment) will bedescribed.

FIG. 1 is a schematic perspective view of a polarized light irradiatingapparatus for photo alignment according to an embodiment of theinvention. The polarized light irradiating apparatus illustrated in FIG.1 is an apparatus configured to perform a photo alignment process onsubstrates S such as liquid crystal substrates each coated with a filmmaterial as works.

Specifically, the apparatus illustrated in FIG. 1 includes irradiatingunits 1 configured to irradiate a preset irradiation area R withpolarized light, stages 21 and 22 on which the substrates S are placed,and a stage movement mechanism 3 configured to move the stages 21 and 22to the irradiation area R to allow the liquid crystal substrates S onthe stages 21 and 22 to be irradiated with the polarized light.

As illustrated in FIG. 1, two irradiating units 1 are provided in theembodiment. The direction of arrangement of the irradiating units 1 isthe direction of movement of the stages 21 and 22. The respectiveirradiating units 1 both have the same configuration, and are configuredto irradiate the polarized light in a substantially rectangular patternR1. Therefore, in the embodiment, a substantially rectangular areaincluding two substantially rectangular irradiating patterns R1 (twoirradiating patterns R1 are included) is set as an irradiation area R.The two irradiating patterns R1 may be or may not be partly overlappedwith each other. As illustrated in FIG. 1, the irradiation area R is anarea included in a horizontal plane.

The stage movement mechanism 3 is a mechanism configured to move thestages 21 and 22 so as to pass through the irradiation area R. In theembodiment, the stages 21 and 22 are arranged in a horizontal position,and the direction of movement is a horizontal direction. Hereinafter,for the sake of convenience of description, the direction of movement ofthe stage movement mechanism 3 is referred to as a length direction, andthe horizontal direction vertical to the direction of movement isreferred to as a width direction.

FIG. 2 is a schematic front view of the polarized light irradiatingapparatus illustrated in FIG. 1. As illustrated in FIG. 2, theirradiating units 1 each include a light source 11, a mirror 12 providedon the rear side of the light source 11, a lamp house 13 including thelight source 11 and the mirror 12 accommodated in the interior thereof,and a polarized light element 14 and the like.

The light source 11 includes a rod-shaped lamp. In the embodiment, sincethe photo alignment is performed with light of an ultraviolet region, ahigh-pressure mercury lamp or a metal halide lamp including other metalsin addition to mercury is used. It is also possible to obtain a longirradiating pattern by arranging a plurality of LEDs configured toradiate light having a wavelength required for the ultraviolet region.The mirror 12 is configured to perform efficient irradiation of thepolarized light, and a gutter-shaped mirror having a shape whichconstitutes part of an oval or a parabolic shape in cross section isused. The longitudinal pair of left and right mirrors are arranged so asto form a slit to achieve a substantially gutter-shaped mirror.

The polarized light element 14 has a function to convert light radiatedfrom the light source 11 into a polarized light required for photoalignment. As the polarized light element 14, a wire grid polarizedlight element provided with fine mesh formed of stripe dielectrics (orconductive or semi-conductor) material on a transparent substrate may beused. The lamp house 13 has a light irradiation port, and the polarizedlight element 14 is arranged at a position between the light source 11and the light irradiation port. A single polarized light element 14 hasa small rectangular shape in many cases, and a configuration in which aplurality of the polarized light elements 14 are arranged in the widthdirection (the length direction of the light source 11) to irradiate theirradiation area R with the polarized light is generally employed. Astructure of being mounted on the lamp house 13 as a unit (polarizedlight element) different from the lamp house 13 may be employed as thepolarized light elements 14. In addition, a filter for adjustingcharacteristics of the polarized light to be irradiated such asselection of the wavelength may be arranged.

In other words, as illustrated in FIG. 1, the apparatus of theembodiment includes the two stages 21 and 22. Hereinafter, the twostages 21 and 22 are referred to as a first stage 21 and a second stage22, respectively. The stage movement mechanism 3 for moving the stages21 and 22 will be described in further detail with reference to FIG. 1,FIG. 2, and FIG. 3. FIG. 3 is a schematic plan view of the stagemovement mechanism 3 illustrated in FIG. 1. FIG. 2 illustrates the stagemovement mechanism 3 illustrated in FIG. 1 together with a controlsystem thereof.

As illustrated in FIG. 1 to FIG. 3, the stage movement mechanism 3includes guide members 31 extending so as to penetrate through theirradiation area R, and drive sources 321 and 322 configured to move thefirst and second stages 21 and 22 along the guide member 31. Asillustrated in FIG. 1 and FIG. 3, two guide members 31 are provided withthe irradiation area R interposed therebetween. The guide members 31,specifically, are linear guides, and extend in parallel to each other.The two stages 21 and 22 are moved by being guided along the two guidemembers 31. In other words, the two guide members 31 are used both as aguide for the first stage 21 and the second stage 22.

A pair of guide blocks 211 are fixed to a lower surface of the firststage 21. The position of fixation of the guide blocks 211 correspondsto the positions of the guide members 31 on both sides. Bearings areprovided in the interior of the guide blocks 211, and the first stage 21is arranged in a state in which the guide members 31 on both sidespenetrate through the guide blocks 211, so that the first stage 21 isguided by the guide members 31. The second stage 22 has the samestructure, and the guide members 31 penetrate through the pair of theguide blocks 221 fixed to the lower surface thereof, whereby themovement of the second stage 22 is guided.

The movements of the respective stages 21 and 22 are performed by thedrive sources 321 and 322 rotating ball screws 331 and 332. In otherwords, as illustrated in FIG. 1 and FIG. 3, the stage movement mechanism3 includes a first ball screw 331 configured to move the first stage 21and a second ball screw 332 configured to move the second stage 22.

One end of the first ball screw 331 is coupled to a first drive source321, and the other end thereof is supported by a bearing 333. In thesame manner, one end of the second ball screw 332 is coupled to a seconddrive source 322, and the other end thereof is supported by a bearing334. The first and second ball screws 331 and 332 are arranged so as toextend in parallel to the direction in which a pair of the guide members31 extend with high degree of accuracy.

A driven block 212 in which the first ball screw 331 is screwed (inwhich the screw is engaged) is fixed to a substantial center of thelower surface of the first stage 21. The first drive source 321 is amotor such as an AC servo motor, and when the first drive source 321rotates the first ball screw 331, the first stage 21 is linearly movedwhile being guided by a pair of the guide members 31. In the samemanner, a driven block 222 in which the second ball screw 332 is screwedis fixed to a substantial center of the lower surface of the secondstage 22, and when the second drive source 322 rotates the second ballscrew 332, the second stage 22 is linearly moved by being guided by apair of the guide members 31.

The polarized light irradiating apparatus of the embodiment includes acontrol unit 4 configured to control the entire apparatus. The controlunit 4 includes a memory 41 in which a sequence program for controllingoperations of respective parts such as the stage movement mechanism 3 ismemorized, and an arithmetic processing unit 42 configured to executethe sequence program. A control signal from the control unit 4 istransmitted to the respective parts of the apparatus including the twodrive sources 321 and 322.

In contrast, the polarized light irradiating apparatus of the embodimentis also provided with a mechanism for mounting the substrates S on thestages 21 and 22 and collecting the substrates S from the stages 21 and22. This point will be described with reference to FIG. 4. FIG. 4 is aschematic perspective view illustrating a mechanism for mounting orcollecting the substrate S on the stage 21 or 22.

For irradiation of the polarized light, the substrate S needs to beplaced on the stage 21 or 22. The substrate S irradiated with thepolarized light needs to be collected from the stage 21 or 22. Suchactions may be performed manually, but generally is performed by a robotin a mass-production line. In this case, a hand of the robot needs to beprevented from interfering with the stage 21 and 22. As a configurationfor this need, the stage 21 and 22 of the embodiment include elevatingpins 5 integrated therein.

In other words, the stages 21 and 22 are each provided with pin holes 50as illustrated in FIG. 4. The pin holes 50 are holes extending in thevertical direction and reach the surfaces of the stage 21 or 22. Threeor four of the pin holes 50 are provided at equivalent positions withrespect to centers of the stage 21 or 22, and the elevating pin 5 arearranged in the interiors of the respective pin holes 50. The respectiveelevating pins 5 are movable upward and downward synchronously with anelevating mechanism, which is not illustrated. When placing thesubstrate S on the stage 21 or 22, the respective pins 5 are movedupward to upper limit positions. In this state, the robot that holds thesubstrate S moves the substrate S upward of the stage 21 or 22, andmoves downward as is, whereby the substrate S is placed on therespective pins. Then, the hand of the robot is retracted, and then therespective elevating pins 5 are moved integrally downward to place thesubstrate S on the stage 21 or 22.

When collecting the substrate S after the irradiation of the polarizedlight, an operation opposite therefrom is performed. The respectiveelevating pins 5 are moved integrally upward to lift the substrate S,and the hand of the robot is inserted into the lower side of the liftedsubstrate S to collect the substrate S. Examples of the mechanismemployed here for transmitting the substrate S to a range where therobot is operable include a lot transport mechanism such as an AGV (AutoGuided Vehicle) or a sheet feed mechanism such as an air conveyer.

The apparatus of the embodiment moves the first and second stages 21 and22 to pass through the irradiation area R alternately by the stagemovement mechanism 3, so that the substrates S on the stages 21 and 22are irradiated with the polarized light alternately. In this case, thestage movement mechanism 3 is configured so that the integrated exposureamount of the polarized light at respective points on the substrate Sdoes not become uneven. This point will be described below withreference to FIG. 3.

In the apparatus of the embodiment, mounting of the substrate S on thefirst stage 21 and collection of the substrate S from the first stage 21are performed at the same position. Hereinafter, this position isreferred to as a first substrate mounting-and-collecting position. Inthe same manner, mounting of the substrate S on the second stage 22 andcollection of the substrate S from the second stage 22 are performed atthe same position. Hereinafter, this position is referred to as a secondsubstrate mounting-and-collecting position. The first substratemounting-and-collecting position is set to one side (the left side asillustrated in FIG. 3, for example) of the irradiation area R, and thesecond substrate mounting-and-collecting position is set to the otherside (the right side as illustrated in FIG. 3, for example) of theirradiation area R.

The stage movement mechanism 3 moves the first stage 21 on which thesubstrate S is mounted to the irradiation area Rat the first substratemounting-and-collecting position and passed therethrough, and then isreturned back. Then, the substrate S is collected from the first stage21 at the first substrate mounting-and-collecting position. The stagemovement mechanism 3 moves the second stage 22 on which the substrate Sis mounted at the second substrate mounting-and-collecting position tothe irradiation area R to and passed therethrough, and then is returnedback. Then, the substrate S is collected from the second stage 22 at thesecond substrate mounting-and-collecting position. For the sake ofconvenience of description, the position at which the first stage 21moved forward changes the direction of movement backward is referred toas a first forward limit position, and the position at which the secondstage 22 moved forward changes the direction of movement backward isreferred to as a second forward limit position. In FIG. 2 and FIG. 3,the first stage positioned at the first forward limit position isillustrated by reference numeral 21′ and the second stage positioned atthe second forward limit position is illustrated by reference numeral22′.

In the apparatus of the embodiment described above, the respectivesubstrate mounting-and-collecting positions are optimized in accordancewith the sizes of the stages 21 and 22 and the position and the size ofthe irradiation area R. In other words, in the apparatus of theembodiment, at least a length of the substrate S on the second stage 22(the length in the direction of movement of the stages 21 and 22) issecured as a space (hereinafter, referred to as a first space) betweenthe first stage 21 positioned at the first substratemounting-and-collecting position and the irradiation area R. In otherwords, the first space is a space which prevents interference with thefirst stage 21 even when the second stage 22′ reaches the second forwardlimit position. Preferably, the length (designated by L1 in FIG. 2) ofthe first space is at least the length of the second stage 22.

At least a length of the substrate S on the first stage 21 is secured asa space (hereinafter, referred to as a second space) between the secondstage 22 positioned at the second substrate mounting-and-collectingposition and the irradiation area R. In other words, the second space isa space which prevents interference with the second stage 22 even whenthe first stage 21′ reaches the first forward limit position.Preferably, the length (designated by L2 in FIG. 2) of the second spaceis at least the length of the first stage 21.

In the embodiment, the first stage 21 and the second stage 22 have thesame size W, and hence a relationship L1=L2>W is satisfied. Morespecifically, for example, when the substrate S has a size on the orderof 1500×1800 mm, the length W of the stages 21 and 22 is on the order of1550×1850 mm, and the value of L1=L2 is on the order of 2600 mm. Thelength of the ball screws 331 and 332 of the stage movement mechanism 3is selected and the movement strokes of the respective stages 21 and 22are set so as to secure the space described above.

The apparatus of the embodiment includes a substrate aligner 6configured to adjust the position or the orientation of the substrate Sso that the irradiation of the polarized light for the photo alignmentis correctly performed. Referring now to FIG. 5, the substrate aligner 6will be described. FIG. 5 is a perspective view illustrating a schematicconfiguration of the substrate aligner 6 provided on the apparatus ofthe embodiment. In FIG. 5, the substrate aligner 6 provided on the firststage 21 is illustrated as an example. However, the second stage 22 hasalso the same configuration. As illustrated in FIG. 5, the first stage21 includes a fixed base 20A and a movable base 20B provided on thefixed base 20A, for example. The driven block 212 and the guide blocks211 described above are members fixed to a lower surface of the fixedbase 20A.

The movable base 20B is provided so as to be movable in the directionsXYθ on the fixed base 20A. In other words, a XYθ movable mechanism 62 isprovided on the fixed base 20A, and the XYθ movable mechanism 62 isconfigured to move the movable base 20B in the XYθ directions for a fineadjustment of the position and the posture of the movable base 20B. TheXY direction in this case is orthogonal directions in a horizontalplane, and, for example, the X-direction corresponds to the lengthdirection (direction of movement), and the Y-direction corresponds tothe width direction. Reference sign θ corresponds to a circumferentialdirection about an axis vertical to the XY direction and, in thisexample, corresponds to a circumferential direction about theperpendicular axis. Since a variety of types of the XYθ movablemechanisms 62 are in the market from various companies, a suitable typecan be selected and integrated. Therefore, detailed description andillustration are omitted.

The XYθ movable mechanism 62 may be used also for the movement of thestage movement mechanism 3 in one of the XY directions, and may beconfigured as an Xθ movable mechanism or a Yθ movable mechanism.

In contrast, the substrates S to be placed on the stages 21 and 22 areeach provided with alignment marks S1. The substrate aligner 6 mainlyincludes alignment sensors 61 configured to take an image of thealignment marks S1 and the XYθ movable mechanism 62, and an alignmentcontrol unit 63 configured to control the XYθ movable mechanism 62 inaccordance with the output from the alignment sensor 61.

The alignment marks S1 are normally provided at predetermined twopositions on each of the substrates S. Two alignment sensors 61 areprovided so as to image the alignment marks S1 at predeterminedpositions in accordance with the positions of the alignment marks S1 andreference positions or a reference directions to be aligned.

For example, as illustrated in FIG. 5, the alignment marks S1 areprovided at two corners along the width direction of the squaresubstrate S. The alignment sensors 61 are arranged above a positionwhere the operation of mounting of the substrate S on the first stage 21is performed (hereinafter referring to as a mounting position). Thepositions of the two alignment sensors 61 correspond to the distancebetween the alignment marks S1 on the substrate S, and the direction ofa line connecting the two alignment sensors 61 corresponds to the widthdirection of the stage movement mechanism 3.

As described above, when the substrate S is mounted on the first stage21, a state in which the respective alignment sensors 61 image therespective alignment marks S1 is achieved. A reference position is setin an imaging area of each of the alignment sensors 61, and thereference position is a position where the center of the alignment markS1 is to be positioned.

The alignment control unit 63 processes output data (image data) fromeach of the alignment sensors 61, and controls the XYθ movable mechanism62 to perform alignment. Specifically, the alignment control unit 63computes data of the distance of movement in the XYθ directions of thesecond stage 22 so that centers of gravity of the alignment marks S1 tobe imaged by the alignment sensors 61 come to the reference positions onthe basis of positional information on the respective alignment marks S1detected by the two alignment sensors 61 and distance information of thetwo alignment marks S1 input in advance in the alignment control unit63, thereby controlling the XYθ movable mechanism 62 and moving themovable base 20B in the XYθ directions. Alignment is now completed.

When the alignment is completed, the line connecting the two alignmentmarks S1 (the width direction of the mounted substrate S) is positionedin the width direction of the stage movement mechanism 3 accurately. Thesubstrate S also takes a predetermined position in the width direction.The predetermined position means, for example, a position at exactly thecenter of the two guide members 31.

The XYθ movable mechanism 62 is configured to fix the position and theposture of the movable base 20B while the substrate S is placed on themovable base 20B. Therefore, the width direction of the substrate Smatches the width direction of the stage movement mechanism 3, and thesubstrate S is moved linearly in the direction of movement andtransported in a state of being located at the predetermined position inthe width direction.

Although it is necessary to position the substrate S roughly at theposition on the movable base 20B, the alignment mark S1 of which isimaged by the alignment sensors 61, this arrangement may just beteaching to the robot when mounting the substrate S by using the robot.When positioning is performed manually, there is a case where a membersuch as a receiving plate is provided on the movable base 20B, and thesubstrate S is arranged in contact therewith to achieve roughpositioning.

The apparatus of the embodiment includes several sensors for confirmingthe positions or the states of the two stages 21 and 22. This point willbe described with reference to FIG. 2.

First of all, a sensor (hereinafter, referred to as a substrate sensor)71 configured to detect the placement of the substrate S is provided inthe interior of the respective stages 21 and 22. The stage movementmechanism 3 includes a sensor (hereinafter, referred to as a first loadposition sensor) 72 configured to detect that the first stage 21 ispositioned at the first substrate mounting-and-collecting position, asensor (hereinafter, referred to as a first limit position sensor) 73configured to detect that the first stage 21 is positioned at a forwardlimit position, a sensor (hereinafter, referred to as a second loadposition sensor) 74 configured to detect that the second stage 22 ispositioned at the second substrate mounting-and-collecting position, anda sensor (hereinafter, referred to as a second limit position sensor) 75configured to detect that the second stage 22 is positioned at a forwardlimit position. Outputs from these sensors 71 to 75 are sent to thecontrol unit 4. The respective sensors 71 to 75 may be selected asneeded from mechanical sensors such as a proximity sensor or a limitswitch, and photo sensors and the like.

Subsequently, a sequence program mounted in the control unit 4 will bedescribed with reference to FIG. 6. FIG. 6 is a drawing for explainingthe sequence program mounted on the control unit 4 and schematicallyillustrating an operation of the apparatus. The following descriptionalso describes an embodiment of a method of irradiating polarized lightfor photo alignment.

In the initial state in which the operation of the apparatus is started,the first stage 21 is at the first substrate mounting-and-collectingposition, and the second stage 22 is at the second substratemounting-and-collecting position as illustrated in the drawing (1) inFIG. 6. In this state, the robot, which is not illustrated in FIG. 6,places the substrate S on the first stage 21. When the substrate sensor71 in the first stage 21 detects the placement of the substrate S and adetection signal is transmitted to the control unit 4, the sequenceprogram activates the substrate aligner 6 for the substrate S on thefirst stage 21. Consequently, the movable base 20B moves in the XYθdirection, and predetermined position and posture of the substrate S areachieved.

Subsequently, the sequence program sends a control signal to the stagemovement mechanism 3 to drive the first drive source 321 to cause thefirst stage 21 to move forward by a predetermined stroke. Thepredetermined stroke corresponds to a stroke by which the first stage 21passes through the irradiation area R and reaches the first forwardlimit position as illustrated in the drawing (2) in FIG. 6. The firstforward limit position is a position where a rear end of the first stage21 matches an end of the irradiation area R or a position a bit forwardthereof.

When the fact that the first stage 21 reaches the first forward limitposition is confirmed by the first limit position sensor 73, thesequence program sends a control signal to the first drive source 321 toinvert the first stage 21 and move the same backward by the same stroke.Accordingly, as illustrated in the drawing (3) in FIG. 6, the firststage 21 returns back to the first substrate mounting-and-collectingposition. During this operation, amounting operation of the substrate Sto the second stage 22 is performed at the second substratemounting-and-collecting position. In other words, the robot places thesubstrate S on the second stage 22 with a predetermined time lag by acontrol signal from the sequence program. On the second stage 22, theplacement of the substrate S is confirmed by the substrate sensor 71 inthe same manner, and then the sequence program activates the substratealigner 6 for the substrate S on the second stage 22 to performalignment. As illustrated in the drawing (3) in FIG. 6, when the firststage 21 returns back to the first substrate mounting-and-collectingposition, the alignment on the second stage 22 is terminated.

In this state, the sequence program sends a control signal to the seconddrive source 322 to drive the second drive source 322 to cause thesecond stage 22 to move forward by a predetermined stroke. Thepredetermined stroke corresponds to a stroke by which the second stage22 passes through the irradiation area R and reaches the second forwardlimit position as illustrated in the drawing (4) in FIG. 6. The secondforward limit position is a position where a rear end of the secondstage 22 matches the end of the irradiation area R or a position a bitforward thereof.

When the fact that the second stage 22 reaches the second forward limitposition is confirmed by the second limit position sensor 75, thesequence program sends a control signal to the second drive source 322to invert the second stage 22 and move the same backward by the samestroke. Accordingly, as illustrated in the drawing (5) in FIG. 6, thesecond stage 22 returns back to the second substratemounting-and-collecting position. During this operation, the fact thatthe first stage 21 is positioned at the first substratemounting-and-collecting position is confirmed by the first load positionsensor 72, and then the substrate S is collected from the first stage 21and a next substrate S is mounted on the first stage 21 at the firstsubstrate mounting-and-collecting position. In other words, the robotremoves the substrate S from the first stage 21, and mounts the nextsubstrate S on the first stage 21.

Then, as illustrated in the drawing (5) in FIG. 6, when the second stage22 is returned back to the second substrate mounting-and-collectingposition, the mounting operation of the next substrate S on the firststage 21 is terminated, and the alignment of the substrate S isterminated. The sequence program emits a control signal again to thefirst drive source 321 and drives the same to move the first stage 21 tothe first forward limit position and return the same again to the firstsubstrate mounting-and-collecting position in a state illustrated in thedrawing (5) in FIG. 6. During this operation, the fact that the secondstage 22 is returned to the second substrate mounting-and-collectingposition is confirmed by the second load position sensor 74, and thenthe substrate S is collected from the second stage 22, a next substrateS is mounted on the second stage 22, and the alignment of the secondstage 22 is performed in the second substrate mounting-and-collectingposition. The operation from then onward is the same, and the sequenceprogram is programmed to perform photo alignment on the two stages 21and 22 alternately by a repetition of the operation as described thusfar by the apparatus. The substrate S is transported by the transportingmechanism such as the AGV or the conveyor to the robot, is subjected tothe photo alignment, and then is transported to the position of theapparatus for the next process by the transporting mechanism.

According to the polarized light irradiating apparatus or method forphoto alignment of the embodiment relating to the configuration andoperation as described above, since the substrates S on the respectivestages 21 and 22 are irradiated with polarized light by the movement ofthe two stages 21 and 22 passing through a single irradiation area Rwhich is irradiated with polarized light alternately, the operation tocollect a substrate S from and to mount a next substrate S on one of thestages 21 and 22 may be performed during the operation to irradiate asubstrate S on the other one of the stages 21 and 22 with polarizedlight. Therefore, the tact time may be reduced significantly, and hencea photo alignment process with higher productivity is achieved.

At this time, a space L1 having at least the length of the substrate Son the second stage 22 is secured between the first substratemounting-and-collecting position and the irradiation area R, and a spaceL2 having at least the length of the substrate S on the first stage 21is secured between the second substrate mounting-and-collecting positionand the irradiation area R. Therefore, the stages 21 and 22 areprevented from interfering with each other, and the respectivesubstrates S are allowed to pass through the irradiation area R.

Suppose that the spaces between the respective substratemounting-and-collecting positions and the irradiation area R have alength smaller than the lengths of the respective substrates S, thesubstrates S cannot pass through the irradiation area R without causingthe interference between the stages 21 and 22. In this case, theexposure amount of the polarized light on an area on the back side ofthe substrate S in the length direction (the direction of movement) isreduced in comparison with other areas, so that uneven photo alignmentprocess results.

Discussing the tact time rather strictly, the relationshipT_(L1)+T_(L2)+T_(L3)≦T_(E1)+T_(E2) is satisfied, where T_(L1) is a timelength required for collecting the substrate S from one of the stages 21and 22, T_(L2) is a time length required for mounting the substrate S onone of the stages 21 and 22, T_(L3) is a time length required foralignment of the mounted substrate S, T_(E1) is a time length requiredfor moving the other one of the stages 21 and 22 from the substratemounting-and-collecting position to the forward limit position, andT_(E2) is a time length for returning the other one of the stages 21 and22 from the forward limit position to the substratemounting-and-collecting position.

However, a configuration in which an outbound movement (a movement fromthe substrate mounting-and-collecting position to the forward limitposition) of one of the stages 21 and 22 follows a homebound movement (amovement returning from the forward limit position back to the substratemounting-and-collecting position) of the other one of the stages 21 and22 is also applicable. In this case, the relationshipT_(L1)+T_(L2)+T_(L3)≦T_(E1) is satisfied. In this configuration, furthershortening of the tact time is achieved.

In the above-described example, although the entire part of a time zoneduring which collection and mounting of the substrate S are performedfor one of the stages 21 and 22 overlaps with a time zone during whichthe movement of the other one of the stages 21 and 22 is performed,partial overlapping is also applicable. In this case, even when themounting of the substrate S in one of the stages 21 and 22 is completed,the movement of the other one of the stages 21 and 22 is not completed.Therefore, there may arise waiting time. If there is the waiting time,the tact time is increased correspondingly. However, the tact time maybe shortened in comparison with the case where there is only one stage,and the productivity is increased.

In the embodiment described above, the respective stages 21 and 22 areirradiated with polarized light when reaching the respective forwardlimit positions and when returning from the respective advancedpositions to the substrate mounting-and-collecting positions, and theboth exposure amounts correspond to the integrated exposure amount.However, this is not a requisite, and a condition in which light isblocked by a shutter or the light source 11 is turned off to achieve astate in which no polarized light is irradiated when returning isapplicable, for example. Be that as it may, if the polarized light isblocked by the shutter, the light source 11 is turned on wastefully, andwhen the light source 11 is turned on and off, an unstable time zoneuntil the lighting state is stabilized is increased. When the polarizedlight is irradiated only in one of outbound and homebound, the speed ofmovement of the stages 21 and 22 is obliged to be reduceddisadvantageously in order to secure the required integrated exposureamount. When the polarized light is irradiated in both the outbound andthe homebound, the speed of movement may be increased and hence theproductivity may further be enhanced without such a problem.

In the apparatus of the embodiment, the operation to cause therespective stages 21 and 22 to pass through the irradiation area R isperformed after the alignment of the substrates S mounted on the stages21 and 22, and hence the orientation of the polarized light axis of theirradiated polarized light matches the predetermined orientation withhigh degree of accuracy. Therefore, the quality of the photo alignmentprocess is further increased.

The orientation of the polarized light axis of the polarized light withwhich the irradiation area R is irradiated is defined by the posture ofthe polarized light elements 14. In the case of the polarized lightelement of the wire grid described above, much polarized light having anelectric field component in the direction vertical to the direction inwhich the wire grid (stripe grid) extends is irradiated, and hence thefilm material is aligned in this orientation. In the apparatus of theembodiment, the polarized light elements 14 are arranged so that thepolarized light axes are oriented in the width direction (the lengthdirection of the light sources 11 in the irradiating units 1) of thestage movement mechanism 3 illustrated in FIG. 1, for example. In thiscase, if the width direction of the substrates S on the stages 21 and 22matches the width direction of the stage movement mechanism 3 with highdegree of accuracy, the film materials on the substrates S are alsophoto-aligned in the width direction with high degree of accuracy. Therespective substrate aligners 6 have a significance in causing thedirection of the photo alignment to match the predetermined directionwith high degree of accuracy as described above.

The accuracy in orientation of the photo alignment is mainly alignmentin the θ direction. However, the alignment in a width direction has asignificance in preventing the substrates S to be transported in a statein which the substrate S is partly protruded from the irradiation areaR. The irradiation area R is set as an area in which the luminance ofthe polarized light in the area is sufficiently uniform. Therefore, ifthe substrate S is protruded out of the area, the luminance of thepolarized light is lowered in the protruded portion, and hence theexposure amount runs short. Therefore, the photo alignment becomesinsufficient at the corresponding portion. In the embodiment, thealignment is also performed in the width direction, such a problem doesnot occur.

In the apparatus of the embodiment, since the pair of guide members 31are also used for moving the first and second stages 21 and 22, theconfiguration of the stage movement mechanism 3 is simplified, and thecost of the apparatus may be reduced. However, a configuration in whichthe first and second stages 21 and 22 are guided by separate guidemembers is also applicable.

Furthermore, the stage movement mechanism 3 may use a linear motor stagewhich floats with air and moves with a magnetic force instead of theball screws. When using the linear motor stage, the guide mechanism maynot be provided.

In the embodiment described above, the position for mounting thesubstrate S and the position for collecting the substrate S of the firststage 21 need to be set on one side of the irradiation area R and theposition for mounting the substrate S and the position for collectingthe substrate S of the second stage 22 need to be set on the other sideof the irradiation area R. However, the mounting position and thecollecting position do not have to be the same position on one side. Thesame applies to the other side. For example, the substrate collectingposition may be set to a position closer to the irradiation area R withrespect to the substrate mounting position on one side. In this case,the substrates S after photo alignment is applied are removed from thestages 21 and 22 at the substrate collecting position, the stages 21 and22 are further retracted to reach the substrate mounting position, wherethe next substrates S are mounted. In this case, as regards thesubstrate collecting position, the above-described spaces L1 and L2 maynot have to be secured without problem.

The two stages 21 and 22 need to pass through the one irradiation area Ralternately. However, the number of the irradiating units 1 does nothave to be two as described above. A configuration in which only oneirradiating unit 1 irradiates the single irradiation area R withpolarized light, and a configuration in which three or more irradiatingunits 1 irradiate the single irradiation area R with polarized light isapplicable.

In the invention of this application, the term “stage” needs to bebroadly interpreted than in the normal case. In other words, there is acase where the substrate S is placed on a plurality of pins having asuction hole such as vacuum contact and is adsorbed onto the pluralityof pins, and the substrate S passes through the irradiation area bymoving the plurality of pins integrally therewith. Therefore, the“stage” needs only to be a member which can move the substrate whileholding the substrate, and does not necessarily have to be a bed-typemember.

As regards the robot, there are a case where a single robot performsmounting and collection of the substrate S between the first and secondstages 21 and 22, and a case where robots are provided for each of thefirst and second stages 21 and 22 to perform mounting and collection ofthe substrate S respectively.

Alternatively, although a liquid crystal substrate with the filmmaterial adhered thereto is assumed as the substrate S, there are a casewhere substrates for display devices other than a liquid crystal displayare irradiated with polarized light for photo alignment as objects, anda case where polarized light is irradiated for the purpose of correctingan angle of view field.

The preceding description has been presented only to illustrate anddescribe exemplary embodiments of the present polarized lightirradiating apparatus and method of irradiating polarized light forphoto alignment. It is not intended to be exhaustive or to limit theinvention to any precise form disclosed. It will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe invention. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from the essential scope. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. The invention may be practiced otherwise than isspecifically explained and illustrated without departing from its spiritor scope.

What is claimed is:
 1. A polarized light irradiating method for photo alignment using a polarized light irradiating apparatus, the apparatus comprising: an irradiating unit configured to irradiate polarized light onto a substrate at an irradiation area; a first stage and a second stage, the substrate is configured to be placed on the first stage or the second stage; and a stage movement mechanism configured to cause the substrate on the first or second stage to be irradiated with the polarized light by moving the first or second stage to the irradiation area; wherein the stage movement mechanism is configured to move the first stage from a first position at one side of the irradiation area to the irradiation area and to move the second stage from a second position at the other side of the irradiation area to the irradiation area; and the stage movement mechanism is configured to return the first stage to the first position after passage through the irradiation area and to return the second stage to the second position after passage of the second stage through the irradiation area; wherein the method comprising: a first movement step and a second movement step; the first movement step comprising: a step (a) of moving the first stage from the first position to the irradiation area; and a step (b) of returning the first stage to the first position from the irradiation area; the second movement step comprising: a step (c) of moving the second stage from the second position to the irradiation area, the step (c) follows after beginning of the step (b); and a step (d) of returning the second stage to the second position from the irradiation area; wherein the step (a) follows after beginning of the step (d).
 2. The polarized light irradiating method according to claim 1, wherein the first stage or a second stage is a plurality of pins, each of the pins comprises a suction hole.
 3. The polarized light irradiating method according to claim 1, wherein the first stage or the second stage includes an XYθ movable mechanism.
 4. The polarized light irradiating method according to claim 1, the method further comprising the steps of: a first mounting step of mounting a first substrate onto the first stage at the first position before the step (a); and a second mounting step of mounting a second substrate onto the second stage at the second position before the step (c).
 5. The polarized light irradiating method according to claim 4, wherein the first position includes a first mounting position, the second position includes a second mounting position; the first mounting step of mounting the first substrate onto the first stage at the first mounting position; and the second mounting step of mounting the second substrate onto the second stage at the second mounting position.
 6. The polarized light irradiating method according to claim 4, the method further comprising the steps of: a first collecting step of collecting the first substrate from the first stage at the first position after the step (b); and a second collecting step of collecting the second substrate from the second stage at the second position after the step (d).
 7. The polarized light irradiating method according to claim 6, wherein the first position includes a first collecting position, the second position includes a second collecting position; the first collecting step of collecting the first substrate from the first stage at the first collecting position; and the second collecting step of collecting the second substrate from the second stage at the second collecting position.
 8. The polarized light irradiating method according to claim 5, a time zone of the first collecting step and the first mounting step and a time zone of the second movement step overlap partially or entirely; and a time zone of the second collecting step and the second mounting step and a time zone of the first movement step partially or entirely overlap.
 9. The polarized light irradiating method according to claim 2, the method further comprising the steps of: a first mounting step of mounting a first substrate onto the first stage at the first position before the step (a); a second mounting step of mounting a second substrate onto the second stage at the second position before the step (c); a first collecting step of collecting the first substrate from the first stage at the first position after the step (b); and a second collecting step of collecting the second substrate from the second stage at the second position after the step (d); wherein, a time zone of the first collecting step and the first mounting step and a time zone of the second movement step partially or entirely overlap; and a time zone of the second collecting step and the second mounting step and a time zone of the first movement step partially or entirely overlap.
 10. The polarized light irradiating method according to claim 3, the method further comprising the steps of: a first mounting step of mounting a first substrate onto the first stage at the first position before the step (a); a second mounting step of mounting a second substrate onto the second stage at the second position before the step (c); a first collecting step of collecting the first substrate from the first stage at the first position after the step (b); and a second collecting step of collecting the second substrate from the second stage at the second position after the step (d); wherein, a time zone of the first collecting step and the first mounting step and a time zone of the second movement step partially or entirely overlap; and a time zone of the second collecting step and the second mounting step and a time zone of the first movement step partially or entirely overlap.
 11. The polarized light irradiating method according to claim 10, the method further comprising the steps of: a first alignment step of moving the first stage in XYθ directions and performing alignment of the first substrate between the first mounting step and the first movement step; and a second alignment step of moving the second stage in the XYθ directions and performing alignment of the second substrate between the second mounting step and the second movement step; wherein a time zone of the first alignment step overlaps a time zone of the second movement step entirely or partly; and a time zone of the second alignment step overlaps a time zone of the first movement step entirely or partly.
 12. A polarized light irradiating method comprising: a first movement step and a second movement step; the first movement step comprising: a step (a) of moving a first stage from a first position to an irradiation area and irradiating a polarized light onto a first substrate mounted on the first stage; and a step (b) of returning the first stage to the first position from the irradiation area; the second movement step comprising: a step (c) of moving a second stage from a second position to the irradiation area and irradiating the polarized light onto a second substrate mounted on the second stage, the step (c) follows after beginning of the step (b); and a step (d) of returning the second stage to the second position from the irradiation area; wherein the step (a) follows after beginning of the step (d).
 13. The polarized light irradiating method according to claim 12, the method further comprising the steps of: a first mounting step of mounting a first substrate onto the first stage at the first position before the step (a); and a second mounting step of mounting a second substrate onto the second stage at the second position before the step (c).
 14. The polarized light irradiating method according to claim 13, the method further comprising the steps of: a first collecting step of collecting the first substrate from the first stage at the first position after the step (b); and a second collecting step of collecting the second substrate from the second stage at the second position after the step (d).
 15. The polarized light irradiating method according to claim 14, a time zone of the first collecting step and the first mounting step and a time zone of the step (c) and the step (d) partially or entirely overlap; and a time zone of the second collecting step and the second mounting step and a time zone of the first movement step partially or entirely overlap.
 16. The polarized light irradiating method according to claim 15, the method further comprising the steps of: a first alignment step of moving the first stage in XYθ directions and performing alignment of the first substrate between the first mounting step and the first movement step; and a second alignment step of moving the second stage in the XYθ directions and performing alignment of the second substrate between the second mounting step and the second movement step; wherein a time zone of the first alignment step overlaps a time zone of the second movement step entirely or partly; and a time zone of the second alignment step overlaps a time zone of the first movement step entirely or partly. 